The present invention relates to a stable liquid formulation of etanercept (recombinant p75 sTNFR:Fc fusion protein), and more particularly, to a liquid formulation comprising one or more stabilizers selected from the group consisting of methionine, lysine, histidine, and pharmaceutically acceptable salts thereof in an amount sufficient to reduce by-product formation of etanercept during storage. The liquid formulation according to the present invention effectively reduces production of etanercept by-products and to stably maintain its pharmaceutical efficacies for long-term storage. Therefore, the reconstitution procedure is not required before administration, and the sterile formulation can be administered to patients to ensure patient safety. Thus, it can be applied to the fields in need of etanercept treatment.